Orthogonal frequency division multiplexing (OFDM) is a basic transmission manner of current wireless communications, where in a range allowed by orthogonality of a subcarrier, a subcarrier interval is compressed to minimum, thereby forming multiple transmission paths that are parallel and do not interfere with each other, so as to improve frequency utilization efficiency of a system. Features of the foregoing OFDM are used in orthogonal frequency division multiple access (OFDMA), and subcarriers in the OFDM that do not interfere with each other are allocated to multiple users, so as to implement multi-user access or data transmission. Sending data in the OFDMA mode is actually: a transmitting end synchronously sends data of multiple receiving ends by using subchannels corresponding to the receiving ends to the receiving ends associated with the subchannels (a subchannel herein may include one subcarrier, or may include multiple subcarriers).
In the prior art, transmission in an OFDMA mode can support only a bandwidth of 20 MHz to perform transmission, and the 20 MHz may be divided into 64 subcarriers, where 48 subcarriers are used for transmitting user data. In a conventional OFDMA technology, a signaling part (a format of the signaling part is only applicable to a bandwidth of 20 MHz) is added following a physical layer preamble in a data format, and the signaling part is used for indicating a user allocated for each subcarrier, where one subcarrier can only correspond to one user identity (ID). A transmitting end synchronously transmits data of different users on different subcarriers, and correspondingly, a user receives, on a corresponding subcarrier, data sent by the transmitting end.
However, when a quantity of users is greater than 48, because of a limitation on the bandwidth of 20 MHz, an indication cannot be performed for rest users beyond 48 users when the rest users receive data of a transmitting end in the prior art.